Asymmetric Mukaiyama Aldol Reactions of Acetyl Phosphonates

Significance

An asymmetric addition of N,O-ketene acetals to acetyl phosphonates, promoted by general Brønsted acid activation is reported. Among several hydrogen-bonding catalysts tested, diol 1 was found to give anti-α-hydroxy phosphonates in good yields and excellent dia­stereo- and enantioselectivities (dr mostly 99:1, er up to 99.5:0.5). Acyclic and hetero-substituted ketene acetals were well tolerated, whereas the enantio-selectivity dropped for cyclic substrates (er = 87.5:12.5). Also acetyl cyanide was used as an electrophile furnishing enantioenriched cyano­silylated ketones.